Ma Zhiying

Assessment of genetic diversity among Chinese upland cottons with Fusarium and/or Verticillium wilts resistance by AFLP and SSR markers

Genetic diversity among 95 Chinese upland cottons with Fusarium and/or Verticillium wilts resistance was estimated using Amplified Fragment Length Polymorphism (AFLP) and Simple Sequence Repeat (SSR) markers. Twenty EcoRI-MseI AFLP and 19 SSR primers with polymorphism were selected to perform the fingerprinting. The results showed that 20 AFLP primer pairs produced a total of 1 480 major bands among 95 genotypes, and 214 were polymorphic bands. The number of total bands per primer pair ranged from 47 to 109, with an average of 74.0. The polymorphism information content (PIC) values for the 20 primer pairs varied from 0.01 (E-ACT/M-CAT) to 0.24 (E-ACA/M-CTA), and the average value was 0.09. Nineteen SSR primers generated 89 DNA bands, of which 61 were polymorphic. The total number of alleles per locus varied from 3 to 8, with an average of 4.7. The average PIC value for the SSR amplification products was 0.69. Genetic similarity estimates for the entire data set ranged from 0.978 to 0.998 based on AFLP and SSR bands. It was proved that the close genetic relationship and narrow genetic diversity existed in the tested cultivars. The clustering patterns could not be correlated to the geographic origin, the pedigree and common parentage of the cultivars.

Evaluation of the introgressed lines and screening for elite germplasm in Gossypium

In this research, 155 cotton introgressed lines from interspecific hybridization have been collected for the purpose of evaluating the effects of enhancement of new upland cotton germplasm by interspecific hybridization, screening for elite germplasm and improving cotton breeding. Through identification of various agricultural traits, we found that different wild cotton species had different capacities in terms of fiber quality, disease resistance, tolerance of abiotic stress, pest resistance and so on. SSR molecular market technology has been used to detect the exotic genetic elements in interspecific hybrids, and 25 SSR specific loci that can be classified into two groups were found among 15 pairs of SSR primers. Results also showed that 8 exotic germplasm (Gossypium barbadense, G. arboreum and G. thurberi, etc) had gen etic transmission toward upland cotton. A strategy of screening elite germplasm with exotic genes based on the molecular marker-assisted breeding techniques was suggested, and 18 lines with high-quality fiber and 4 lines with resistance to Fusanrium wilt and Verticillium wilt have been obtained.

Island Cotton Enhanced Disease Susceptibility 1 Gene Encoding a Lipase-Like Protein Plays a Crucial Role in Response to Verticillium dahliae by Regulating the SA Level and H2O2 Accumulation

Cotton is one of the most economically important crops, but most cultivated varieties lack adequate innate immunity or resistance to Verticillium wilt. This results in serious losses to both yield and fiber quality. To identify the genetic resources for innate immunity and understand the pathways for pathogen defenses in this crop, here we focus on orthologs of the central Arabidopsis thaliana defense regulator Enhanced Disease Susceptibility 1 (EDS1). The full-length cDNA of GbEDS1 was obtained by screening the full-length cDNA library of Gossypium barbadense combining with RACE strategy. Its open reading frame is 1848 bp long, encoding 615 amino acid residues. Sequence analysis showed that GbEDS1 contains a conserved N-terminal lipase domain and an EDS1-specific KNEDT motif. Expression profiling indicated that the gene is induced by Verticillium dahliae as well as salicylic acid (SA) treatment. Subcellular localization assays revealed that GbEDS1 is located in the cell cytoplasm and nucleus. Overexpression of GbEDS1 in Arabidopsis dramatically up-regulated SA and H2O2 production, resulting in enhanced disease resistance to V. dahliae. Silencing of GbEDS1 in G. barbadense significantly decreased SA and H2O2 accumulation, leading to the cotton more susceptibility. Moreover, combining the gene expression results from transgenic Arabidopsis and silenced-GbEDS1 cotton, it indicated that GbEDS1 could activate GbNDR1 and GbBAK1 expression. These findings not only broaden our knowledge about the biological role of GbEDS1, but also provide new insights into the defense mechanisms of GbEDS1 against V. dahliae in cotton.